The invention relates to the field of food-processing and similar industries, and more particularly relates to devices for securing to a shaft of a machine.
The food processing industry and other similar industries, require equipment and systems which often include components which are coupled to a shaft. Typically, many of those components are secured to a shaft, or two shafts are coupled to each other, by way of a conventional shaft collar or shaft coupling. Shaft collars and shaft couplings in such equipment and systems, have been particular elements affording locations for accumulating debris, as well has harboring contaminants and breeding grounds for bacteria, as well as other harmful organisms.
Particularly with respect to food processing, it is important that equipment and systems the amenable to periodic thorough cleaning and decontamination, and also be operative in an environment in which contaminants, bacteria and other harmful organisms are absent, or at least controlled to acceptable levels. Government regulation and requirements on food safety are directed to the design and performance of equipment and systems in this field.
However, despite increased government regulation and requirements on food safety in the past few decades, no shaft collars or shaft couplings are currently available for use on food processing equipment and systems, which are designed to adequately meet the food industry's unique set of requirements. The prior art “solution”, albeit sub-optimal and inadequate, is the use of common collar designs produced in specialized materials—specifically FDA/USDA-approved polymers, such as acetal resin, and stainless steel alloys, typically of the 316 formulation. The main purpose for using these materials is their ability to resist the corrosion that can be caused by the chemicals used in a conventional washdown process.
The mechanical design of conventional collars, and their interface with the rotating shafts upon which they are mounted, simply does not address, except in a very general fashion, minimization of the possibility of particle entrapment and the resulting potential for bacterial growth in and around the collar.
In conventional practice, end users looking to minimize the potential of bacteria growth often settle for the disadvantages of a set screw-type collar (due to the reduced number of physical features) and seal the set screw in place with a silicon RTV or similar material once the collar is secured to a shaft. Such a configuration greatly hampers the user's ability to later adjust the collar. Moreover, it is well known that with the use of set screw collars, the shaft to which the collar is affixed is easily damaged by the set screw. In addition, the holding power of a set screw collar is considerably less than that of other types of comparable-sized collars, such as clamp collars. As a consequence of such issues with set screw collars, many users have also eliminated the set screw features completely from their design, instead relying on a press fit between the shaft and collar to maintain positioning.
Regardless of the type of collar or coupling, the prior art collars and couplings used in the food industry have a large number of exposed physical features which pose a high risk for collecting food particles and the subsequent potential for the growth of harmful bacteria that feed on the stray food particles lodged in those physical features. As a consequence, designers of food processing equipment have gone to great lengths to reduce and/or eliminate physical features of the machinery that present the possibility for food entrapment, often cordoning off as much of the overall machine as possible behind shielding in order to minimize the number of components that can possibly come into contact with the food product. Components located outside such shielding, which often include shafts and associated collars and couplings secured thereto, are subject to the strict government safety equipment regulations. Machine components within the contact area, must be cleaned frequently and thoroughly, with great expense of both labor and machine down-time, else the operator runs the risk of hefty consequences from a failed inspection by a regulatory agency. The conventional collars and couplings which are commonly used as guides, stops and couplings in such machines, often account for a significant amount of the cleaning time due to the numerous small crevices created by the screw features and clamping cuts.
Conventional modifications made to collars and couplings to decrease the likelihood of food entrapment and consequent bacteria growth, come with great sacrifices in performance characteristics. The method previously described for the use of set screw collars not only introduces the negative aspects of set screw collars (i.e., damage to shafts, lower holding power than clamp styles), but also severely inhibits the user's ability to adjust or remove the collar. While press-fit collars generally have few or no entrapment areas besides the collar/shaft or coupling/shaft interface, their holding power for both axial and radial loads are significantly lower than conventional clamp-type shaft collars and shaft couplings, and rapid or precise position adjustments are not feasible.
Improved shaft collars and shaft couplings are needed for application in equipment and systems used in the food processing and related industries, to provide improved food safety as well as more efficient operation.